1. Field of the Invention
The present invention relates to the art of fabricating corrugated paper or plastic board. More particularly, the present invention represents an improvement in mounting and connecting the numerous vacuum tubes on a fingerless corrugating machine which are used to evacuate the circumferential hold-down grooves in a lower corrugating roll surface.
2. Prior Art
Single-faced corrugated plastic or paper board is traditionally fabricated in a cooperating 3-roll set which includes two fluted surface rolls and a smooth surface roll. The two fluted rolls are aligned and positioned for meshing flute rotation. A continuous web of paper is drawn into the meshing nip of the two fluted rolls to be formed by pressure and heat into an undulating continuum.
Upon emergence from the meshing flute nip, the corrugated web is held tightly against the fluted profile of one of the fluted rolls, called the "lower corrugating roll," and carried about an arcuate transition zone to a second nip position corresponding with the smooth surface roll. Here, a second, flat web is drawn into this second nip to be adhesively bonded along the crest line of each flute. The resulting product is called "single-faced board."
In the arcuate transition zone between the first, corrugating nip and the second, single-facing nip, it is necessary to hold the corrugated web, by some positive confining means, tightly against the lower corrugating roll surface profile. The currently preferred confining means is by an induced pressure differential. Numerous, thirty to fifty, circumferential grooves are cut into the fluted surface profile of the lower corrugating roll. From the side of the roll opposite from the arcuate transition zone, two vacuum tubes are inserted in each groove; one on each diametric side of the groove. By means of a conduit connected vacuum pump, these tubes partially evacuate the atmosphere between the corrugated web and the roll surface profile. The pressure of the external atmosphere consequently presses the web tightly against the lower corrugating roll fluted profile surface.
In the course of single-faced board production, these vacuum tubes are quickly worn or damaged to require frequent replacement. Since the entire machine is hot and crowded, tube replacement is a hazardous, tedious manual task sometimes requiring the rotation of a tubing nut such as that disclosed by U.S. Pat. No. 4,368,094 to Johann Mayer et al. A few installations rely upon quick connecting fluid couplings which require a machined vacuum tube tip portion for insertion into the coupling housing. Due to the frequency of replacement and the cost of machine working, this technique represents an extravagant solution to the tube replacement problem.
It is, therefore, an objective of this invention to provide an inexpensive means for rapid assembly and disassembly of corrugating machine vacuum tubes.
Another object of the present invention is to provide an inexpensively fabricated vacuum tube.
Another object of the present invention is to provide a vacuum tube holder that securely sockets the tube without threaded fasteners or machined surfaces.